The present invention is generally directed to toners, and toner processes, and more specifically, to a process which comprises the aggregation of latex resin particles with colorant, especially pigments, and optionally additive toner particles into toner sized aggregates, followed by coalescence or fusion by heating of the resulting aggregates to form integral toner particles, and thereafter, washing with a base component, and more specifically, wherein washing is accomplished with, for example, a base of an alkali metal hydroxide subsequent to coalescence thereby enabling, for example, improved toner triboelectric charging characteristics and excellent batch to batch reproducibility. In embodiments, the present invention is directed to a chemical in situ process for generating toners without resorting to conventionally known pulverization and classification methods, thus rendering the process economical, and wherein toner compositions can be obtained with a particle size as herein illustrated by volume average diameter of, for example, from about 1 to about 25, and preferably from 2 to about 10 microns, and narrow particle size distribution as conventionally characterized by GSD (geometric standard deviation) of, for example, from about 1.10 to about 1.35, and more specifically, from about 1.15 to about 1.25 as measured on the Coulter Counter. The resulting toners can be selected for known electrophotographic imaging and printing processes.
The size of the formed aggregates is primarily dependent on the temperature at which aggregation is accomplished, and for a particular latex composition, larger aggregates can be obtained at higher temperatures, provided that the temperature is not substantially above the Tg (glass transition temperature) of the latex resin. Also, the particle size distribution of the aggregates does not appear to be primarily dependent on the aggregation temperature, and this size is generally narrow as typified by a GSD of less than about 1.35, and more specifically, of less than about 1.25. These aggregates, which for example, have a volume average diameter of about 1 to 20 microns, are then subjected to further heating, optionally in the presence of additional anionic surfactant at a temperature above equal to about, or about the Tg of the resin, and more specifically, at a temperature ranging from about 10.degree. C. to about 50.degree. C. above the Tg for an effective time period, for example about 2 hours in embodiments, to effect fusion or coalescence of the latex particles within the aggregates affording integral toner particles. The degree of coalescence is dependent, for example, on the temperature and duration of the heating. Suitable temperatures for coalescence range, for example, from about equal to, or slightly above the resin Tg to in excess of about 100.degree. C., depending on the nature of the latex resin, its composition, and the colorant and optional additives. In general, the coalescence is conducted at a temperature of between about 65.degree. C. to about 110.degree. C., and preferably between about 75.degree. C. to about 105.degree. C. The resulting toner particles retain the size of the precursor aggregates, that is, the volume average particle size of the aggregate is preserved during coalescence wherein electrostatically bound aggregates are converted to integral toner particles as a result of the fusion of the resin particles within the aggregate particles. Subsequently, the toner is formed into a slurry with a base, followed by mixing and washing the toner.